I had a set of Egge high compression pistons made in the early seventies. I installed them in an engine but sold the car long ago, and removed the pistons before firing the engine and selling the car. I have sold them to a buyer and he and his machine shop have asked me what the recommended clearance is on them. Being that they are fifty years old, I haven't got a clue what the factory recommendation is. I could just give him Egge's number, unless someone here knows the answer.
yeah prolly should call egge, that way if they have a problem they can call them.
but i would say err to the side looser rather than tight.
Come on guys. Isn't anyone using Egge pistons?
all 3 of my T's have EGGE hi-compression pistons, gapping is 0.004 - 0.006 " per inch of bore, l always use the lower figure and end up with about 0.016 - 0.018" on the ring ( I also buy the next oversize ring and hand file back ).
PS the cast iron pistons used a smaller gapping.
Dooooh ! brain fade - that's the ring gapping, sorry......the pistons l use similar numbers 0.006 - 0.008 " ( from memory ), no slap. no jamm.
Best off to call Egge:
The reason being if they are older pistons then they would know what kind of aluminum they were made from and can suggest the right piston clearance as someone has already mentioned above.
Egge recommends .003 thousandths clearance for their pistons. As far as the ring gaps they should be a minimum of .004 thousandths per inch of cylinder bore.
I reckon .003" is a little tight for aluminium... try .004" to .005"
Anthony, Jim Ketchum, who posted above you, works for Egge, or used to.
The replacement aluminum pistons I get from the vendors have the .003" clearance printed on the box. But the local old-time (3rd generation) engine shop here always bores Model T and A blocks out to .005" more than the piston size for aluminum pistons, and they won't bore one without having a new piston in hand. They say the pistons and cylinders will be scored at .003" clearance. I've had them bore several for me, and they always came out great.
I've had Egge pistons score the cylinder walls at .003" Rods were aligned with pistons attached. Problem eliminated when clearance increased to .005". I think Egge's recommendation is generic to all their pistons. Its too close for Model Ts IMHO
Egge's spec sheet says 0.0025 clearance across thrust surfaces. That's plural. The thrust surface (one) is shown as the side of the piston. That means 0.005 or 0.025 on each side of the piston.